FIG. 1 is a synchronization principle diagram illustrating FSS in a Long Term Evolution (LTE) system in the prior art. As shown in FIG. 1, an over-the-air signal received by a receiver is sent to a Reference Signal (RS) extracting and descrambling module via a Radio Frequency (RF) identification module and a Fast Fourier Transformation (FFT) module to generate RS signal sets {RS(l)}0x and {RS(l)}1x respectively on lth Orthogonal Frequency Division Multiplexing (OFDM) symbols on a receiving antenna 0-transmitting antenna x pair and a receiving antenna 1-transmitting antenna x pair. Each receiving-transmitting antenna pair sends the RS signal sets {RS(l)}0x and {RS(l)}1x of the lth OFDM) symbol into an Inverse Discrete Fourier Transform (IDFT) module to respectively perform operation, and performs calculation of modulus on an operation result of the IDFT module to obtain Channel Impulse Response (CIR) estimations {CIR(l)}0x and {CIR(l)}1x of the lth OFDM symbol on each receiving-transmitting antenna pair. Here, the calculation of modulus is performed on the operation result of the IDFT module to avoid performance degradation caused by coherent accumulation under an actual fast fading channel. In order to increase the Signal-to-Noise Ratio (SNR) of the CIR estimations {CIR(l)}0x and {CIR(l)}1x, ‘continuous’ {CIR(l+•)}0x and {CIR(l+•)}1x will be generally accumulated by a time accumulator to obtain {CIRave}0x and {CIRave}1x, which are inputted to a subsequent FSS detection module. The FSS detection module detects an FFT windowing initial point startnx of a receiving antenna n on each receiving-transmitting antenna pair independently, and defines forward shift of an FFT window as a negative value, and backward shift of the FFT window as a positive value. All transmitting antenna port detection results on one transmitting antenna port are sent to an FSS combining module to generate an FFT initial point startn of a certain receiving antenna port. A synthetic FFT initial point startn of each receiving antenna generates a final FFT initial point control signal FFT_startn to the FFT module eventually through a loop filter.
A conventional method for detecting FSS is to perform threshold search, peak search push-forward or calculation of center of gravity push-forward etc. on a CIR time accumulation result {CIRave}nx each receiving-transmitting antenna pair. Generally, a subsequent Rxn FSS combining module simply searches for and outputs a minimum in {startnx}.
When the conventional method for detecting FSS and the combining method are applied in an LTE Multiple-Input and Multiple-Output (MIMO) system, a relatively large error will be caused in the case of a power abnormality of a certain transmitting antenna. For example, in a laboratory test, a receiver is configured with N transmitting antennas and two receiving antennas. However, a cable is really only connected on Rx0-Tx0 and Rx1-Tx1 antenna pairs. An FSS detection result of Rx0-Tx1˜N-1 antenna pairs without a cable is substantially a random number, which will seriously interfere with an output of the FSS combining module, thereby increasing a startn output noise. In an actual outfield test, since extremely low power of a certain transmitting antenna port m is caused by abnormality of a base station, the SNR of a CIR time accumulation result on a Rxn-Txm antenna pair is affected, thus increasing the output noise during FSS detection.